1. Field of the Invention
This invention relates to normally liquid lubricating oil additives which are multifunctional additives providing anti-oxidant, diesel deposit inhibition, and friction modifying properties when added to lubricating oil. In particular, this invention relates to C.sub.14 to C.sub.18 alkyl catechol lubricating oil additives which are normally liquid at typical storage temperatures. The alkyl catechols of this invention are useful multifunctional lubricating oil additives providing anti-oxidant, diesel deposit inhibition, and boundary friction-reducing properties for the lubricating oil.
2. Prior Art
Certain alkyl catechols are known in the art as anti-oxidant additives for lubricating oils. In particular, Wright, U.S. Pat. No. 2,429,905, discloses para-substituted stearylcatechol and other para-substituted lower alkyl catechols as possessing anti-oxidant properties. Similarly, Andress et al., U.S. Pat. No. 3,554,945, discloses polyhydroxy benzenoid compounds as useful antioxidant additives for lubricating oils. Although alkylated products prepared from a C.sub.15 -C.sub.20 mixed olefin fraction are disclosed, Andress et al. do not specifically disclose C.sub.15 -C.sub.20 monoalkylated catechols or that alkyl catechol compositions would possess friction modifying properties.
Thomas et al., U.S. Pat. No. 2,795,548, is another prior art reference which discloses alkyl catechols. In particular, Thomas et al. disclose alkyl catechols containing 2 to 18 carbon atoms in the alkyl group which are employed as intermediates in the preparation of borated alkyl catechols.
In addition to their anti-oxidant and diesel deposit inhibition properties, it has now been found that longer chain monoalklyl catechol of 14 carbon atoms or more possess improved boundary friction-reducing properties than do shorter chain monoalkyl catechols (those of less than 14 carbon atoms). Accordingly, when employing alkyl catechol additives in a lubricating oil, it is desirable to employ longer chain alkyl catechols.
However, there is a problem with the use of longer chain alkyl catechols since the preparation of these catechols often results to some degree in the occurrence of solidification or haziness in the product. The degree of this problem ranges from alkyl catechols which are a solid wax at room temperature to liquid alkyl catechols containing wax particles at room temperature. In any case, the solidification or haziness requires that prior to formulation the solid particles or haziness must be removed by either heating the alkyl catechol which adds an additional step to the overall process or by adding sufficient diluent oil to the alkyl catechol which increases the cost of transporting this additive.
Although shorter chain alkyl catechols would alleviate this solidification problem, the use of these shorter chain alkyl catechol would be at the expense of improved boundary friction. Accordingly, there is a need to develop an alkyl catechol which is normally liquid at typical storage temperatures while maintaining sufficient alkyl chain length to impart multifunctional properties such as anti-oxidant, diesel deposit inhibition, and boundary friction-reducing properties to the lubricant oil.
It has now been found that C.sub.14 to C.sub.18 monoalkyl catechols prepared from a mixture of at least three C.sub.14, C.sub.15, C.sub.16, C.sub.17, and C.sub.18 linear alpha-olefins and containing less than 20% C.sub.18 alkyl content are normally liquid at typical storage temperatures. Moreover, the C.sub.14 to C.sub.18 alkyl chain length imparts multifunctional properties to the lubricating oil. The liquid characteristic of the C.sub.14 to C.sub.18 monoalkyl catechols of this invention is particularly surprising in view of the fact that a monoalkyl catechol prepared from a mixture of C.sub.18, C.sub.19, C.sub.20 and C.sub.21 linear alpha-olefins, as well as those prepared from a mixture of C.sub.14, C.sub.16 and C.sub.18 linear alpha olefins with greater than 20% C.sub.18 content contain some solidification.